Constant k filters, also k-type filters, are a type of electronic filter designed using the image method. They are the original and simplest filters produced by this methodology and consist of a ladder network of identical sections of passive components. Historically, they are the first filters that could approach the ideal filter frequency response to within any prescribed limit with the addition of a sufficient number of sections. However, they are rarely considered for a modern design, the principles behind them having been superseded by other methodologies which are more accurate in their prediction of filter response. (Full article...)
The primary line constants are parameters that describe the characteristics of conductive transmission lines, such as pairs of copper wires, in terms of the physical electrical properties of the line. The primary line constants are only relevant to transmission lines and are to be contrasted with the secondary line constants, which can be derived from them, and are more generally applicable. The secondary line constants can be used, for instance, to compare the characteristics of a waveguide to a copper line, whereas the primary constants have no meaning for a waveguide.
Filters are required to operate at many different frequencies, impedances and bandwidths. The utility of a prototype filter comes from the property that all these other filters can be derived from it by applying a scaling factor to the components of the prototype. The filter design need thus only be carried out once in full, with other filters being obtained by simply applying a scaling factor. (Full article...)
The Yamaha NS-10 studio monitor, identifiable by its horizontal lettering and distinctive white cone.
The Yamaha NS-10 is a loudspeaker that became a standard nearfield studio monitor in the music industry among rock and pop recording engineers. Launched in 1978, the NS-10 started life as a bookshelf speaker destined for the domestic environment. It was poorly received but eventually became a valuable tool with which to mix rock recordings. The speaker has a characteristic white-coloured mid–bass drive unit.
Technically, it is known as a speaker that easily reveals poor quality in recordings. Recording engineers sought to dull its treble response by hanging tissue paper in front of it, resulting in what became known as the "tissue paper effect" – a type of comb filtering. The NS-10 has been used to monitor a large number of successful recordings by numerous artists, leading Gizmodo to refer to it as "the most important loudspeaker you never heard of". (Full article...)
The original ESL, in production between 1957 and 1985, has been hailed in Sound & Vision as one of the most important speakers of the 20th century. It was succeeded in 1981 by the ESL-63, which remained in production until 1999. As of 2013, Quad maintains four electrostatic speakers in its range. (Full article...)
A 10 dB 1.7–2.2 GHz directional coupler. From left to right: input, coupled, isolated (terminated with a load), and transmitted port.
Power dividers (also power splitters and, when used in reverse, power combiners) and directional couplers are passive devices used mostly in the field of radio technology. They couple a defined amount of the electromagnetic power in a transmission line to a port enabling the signal to be used in another circuit. An essential feature of directional couplers is that they only couple power flowing in one direction. Power entering the output port is coupled to the isolated port but not to the coupled port. A directional coupler designed to split power equally between two ports is called a hybrid coupler.
Directional couplers are most frequently constructed from two coupled transmission lines set close enough together such that energy passing through one is coupled to the other. This technique is favoured at the microwave frequencies where transmission line designs are commonly used to implement many circuit elements. However, lumped component devices are also possible at lower frequencies, such as the audio frequencies encountered in telephony. Also at microwave frequencies, particularly the higher bands, waveguide designs can be used. Many of these waveguide couplers correspond to one of the conducting transmission line designs, but there are also types that are unique to waveguide. (Full article...)
First-generation "chrome bumper" Naim NAIT
The Naim NAIT (acronym for "Naim Audio Integrated amplifier") is an integrated amplifier from the British hi-fi manufacturer, Naim Audio. The original NAIT is one of the most recognisable pieces of hi-fi equipment ever made. Hi-fi critic Lucio Cadeddu recognised its legendary status, referring to it as "one of the most controversial and famous integrated amps in the history of HiFi".
Sinclair Scientific calculator photographed c. 1974
The Sinclair Scientificcalculator was a 12-function, pocket-sized scientific calculator introduced in 1974, dramatically undercutting in price other calculators available at the time. The Sinclair Scientific Programmable, released a year later, was advertised as the first budget programmable calculator.
Significant modifications to the algorithms used meant that a chipset intended for a four-function calculator was able to process scientific functions, but at the cost of reduced speed and accuracy. Compared to contemporary scientific calculators, some functions were slow to execute, and others had limited accuracy or gave the wrong answer, but the cost of the Sinclair was a fraction of the cost of competing calculators. (Full article...)
Late model (c.1998) LS3/5A from Spendor, one of the BBC licensees
The LS3/5A (each element pronounced separately, without the stroke) is a small studio monitor loudspeaker originated by the BBC for use by outside broadcast vans to ensure quality of their broadcasts. The speaker concept set out transparent and natural sound as the goal, and the achievement of the end result is widely acknowledged.
The BBC granted licences to a small number of British firms, who first manufactured the product in 1975. The product underwent a change in 1987 due to consistency issues in manufacturing, and again in around 2003 when original parts from KEF ran out. Upwards of 60,000 pairs of the speaker have been sold. Reviewers have recognised its enormous importance as a bookshelf design. (Full article...)
The image method of filter design determines the properties of filter sections by calculating the properties they have in an infinite chain of such sections. In this, the analysis parallels transmission line theory on which it is based. Filters designed by this method are called image parameter filters, or just image filters. An important parameter of image filters is their image impedance, the impedance of an infinite chain of identical sections. (Full article...)
This approach is especially useful in the design of mechanical filters—these use mechanical devices to implement an electrical function. However, the technique can be used to solve purely mechanical problems, and can also be extended into other, unrelated, energy domains. Nowadays, analysis by analogy is a standard design tool wherever more than one energy domain is involved. It has the major advantage that the entire system can be represented in a unified, coherent way. Electrical analogies are particularly used by transducer designers, by their nature they cross energy domains, and in control systems, whose sensors and actuators will typically be domain-crossing transducers. A given system being represented by an electrical analogy may conceivably have no electrical parts at all. For this reason domain-neutral terminology is preferred when developing network diagrams for control systems. (Full article...)